1. Field of the invention
The present invention relates to an improved structure of a computer mouse, and particularly, to an improved Z axis device which can be simply assembled and reduce costs in manufacturing the computer mouse.
2. Description of the Prior Art
A traditional computer mouse for generating a 2-dimentional cursor control signal usually comprises X, Y optical wheels and Z axis device. An X-shaft and a Y-shaft orthogonally extend from the center portion of each of the X-wheel and the Y-wheel, respectively, while the X-shaft and the Y-shaft are perpendicular to each other. The Z axis device is located at a 45 degree position correspondent to the X-shaft and the Y-shaft.
During the rotation of the roller ball of the computer mouse, the X-shaft and the Y-shaft have to be constantly in contact with the roller ball so that the X-wheel and the Y-wheel can be simultaneously rotated with the roller ball. The cursor control signal will be wrongly detected if the aforementioned simultaneous rotation is not well maintained. To keep close contact between the X-shaft, the Y-shaft and the roller ball, one of the methods is to press the roller ball toward the X-shaft and the Y-shaft via the Z axis device's force.
A prior Z axis device, which is illustrated in FIG. 1, comprises a Z axis roller 10, a positioning slot 11 and a roller base 12. The Z axis roller 10 is mounted on the roller base 12 and the roller base 12 is suspended in the positioning slot 11. Then the two ends of a spring 13 are engaged with the roller base 12 and the positioning slot, respectively, thus to assemble the Z axis device which is shown in FIG. 2.
The Z axis device depicted above comprises more components which will consume higher costs as expected.